Stopping prednisone

TLDR how bad is it to stop prednisone kinda quickly?

I(19ftm) have been taking prednisone for 5 years now and have been stuck at 15mg for about a year now. I take pred(,leflunomide and rinvoq if it matters) for Juvenile Idiopathic Arthritis and have tried nearly every mode of medication for this(methotrexate, tocilizumab, rituximab, Orencia) with initial success at first but eventually something showed that the treatment hadn’t worked enough. I currently am an ambulatory wheelchair user from an unknown reason(I have severe muscle pain and fatigue but my muscles are perfectly fine apparently and my blood levels are too) which exacerbates the pain that my large chest already causes. I give this background to say that me and my arthritis have had a long journey that we are still on.

I recently had a consult with a surgeon to get top surgery. He said that with my conditions, medication and weight that I would almost 100% have complications post-op. Over these past 5 years I’ve gained 50kg(110lb) and do not have a good relationship with my body but no matter how much I count calories in and out I stay the same weight. I have so much scar tissue from stretch marks and my skin is just generally so much more fragile and stretchy than it should be for this big of a surgery. I honestly don’t hate being fat aesthetically(like in a bear way) but I think I’d be more comfortable like 10-15kg lighter. I bring this up for a couple reasons, #1 is that I want to make it clear how prednisone has messed me, #2 that I really need to get this for surgery for both my mental and physical health.

Losing weight is nearly impossible on prednisone as I’m sure many of you know. I really want to be off of it as soon as I can so I can start the process of losing weight. I don’t know much about how prednisone works but I know that weaning is a very long process. Why can’t I wean -5mg per week? What exactly is prednisone doing in my body and why is stopping it to fast so bad?

P.S I do apologize if this feels disjointed and/or ramble-y, I wrote certain parts out of order and reorganized them